This invention relates to fire extinguishing compositions comprising at least one fluorinated ketone compound and to processes for extinguishing, controlling, or preventing fires using such compositions, for making alpha-branched fluorinated ketones, and for purifying such ketones.
Various different agents and methods of fire extinguishing are known and can be selected for a particular fire, depending upon its size and location, the type of combustible materials involved, etc. Halogenated hydrocarbon fire extinguishing agents have traditionally been utilized in flooding applications protecting fixed enclosures (e.g., computer rooms, storage vaults, telecommunications switching gear rooms, libraries, document archives, petroleum pipeline pumping stations, and the like), or in streaming applications requiring rapid extinguishing (e.g., military flight lines, commercial hand-held extinguishers, or fixed system local application). Such extinguishing agents are not only effective but, unlike water, also function as xe2x80x9cclean extinguishing agents,xe2x80x9d causing little, if any, damage to the enclosure or its contents.
The most commonly-used halogenated hydrocarbon extinguishing agents have been bromine-containing compounds, e.g., bromotrifluoromethane (CF3Br, Halon(trademark) 1301) and bromochlorodifluoromethane (CF2ClBr, Halon(trademark) 1211). Such bromine-containing halocarbons are highly effective in extinguishing fires and can be dispensed either from portable streaming equipment or from an automatic room flooding system activated either manually or by some method of fire detection. However, these compounds have been linked to ozone depletion. The Montreal Protocol and its attendant amendments have mandated that Halon(trademark) 1211 and 1301 production be discontinued (see, e.g., P. S. Zurer, xe2x80x9cLooming Ban on Production of CFCs, Halons Spurs Switch to Substitutes,xe2x80x9d Chemical and Engineering News, page 12, Nov. 15, 1993).
Thus, there has developed a need in the art for substitutes or replacements for the commonly-used, bromine-containing fire extinguishing agents. Such substitutes should have a low ozone depletion potential; should have the ability to extinguish, control, or prevent fires or flames, e.g., Class A (trash, wood, or paper), Class B (flammable liquids or greases), and/or Class C (electrical equipment) fires; and should be xe2x80x9cclean extinguishing agents,xe2x80x9d i.e., be electrically non-conducting, volatile or gaseous, and leave no residue. Preferably, substitutes will also be low in toxicity, not form flammable mixtures in air, have acceptable thermal and chemical stability for use in extinguishing applications, and have short atmospheric lifetimes and low global warming potentials. The urgency to replace bromofluorocarbon fire extinguishing compositions is especially strong in the U.S. military (see, e.g., S. O. Andersen et al., xe2x80x9cHalons, Stratospheric Ozone and the U.S. Air Force,xe2x80x9d The Military Engineer, Vol. 80, No. 523, pp. 485-492, August, 1988). This urgency has continued throughout the 1990s (see US Navy Halon 1211 Replacement Plan Part 1xe2x80x94Development of Halon 1211 Alternatives, Naval Research Lab, Washington, D.C., Nov. 1, 1999).
Various different fluorinated hydrocarbons have been suggested for use as fire extinguishing agents. However, to date, we are unaware that any fluorinated ketone having zero, one, or two hydrogen atoms on the carbon backbone has been evaluated as a fire-fighting composition.
In one aspect, this invention provides a process for controlling or extinguishing fires. The process comprises introducing to a fire or flame (e.g., by streaming or by flooding) a non-flammable extinguishing composition comprising at least one fluorinated ketone compound containing up to two hydrogen atoms. Preferably, the extinguishing composition is introduced in an amount sufficient to extinguish the fire or flame. The fluorinated ketone compound can optionally contain one or more catenated (i.e., xe2x80x9cin-chainxe2x80x9d) oxygen, nitrogen or sulfur heteroatoms and preferably has a boiling point in the range of from about 0xc2x0 C. to about 150xc2x0 C.
The fluorinated ketone compounds used in the process of the invention are surprisingly effective in extinguishing fires or flames while leaving no residue (i.e., function as clean extinguishing agents). The compounds can be low in toxicity and flammability, have no or very low ozone depletion potentials, and have short atmospheric lifetimes and low global warming potentials relative to bromofluorocarbons, bromochlorofluorocarbons, and many substitutes therefor (e.g., hydrochlorofluorocarbons, hydrofluorocarbons, and perfluorocarbons). Since the compounds exhibit good extinguishing capabilities and are also environmentally acceptable, they satisfy the need for substitutes or replacements for the commonly-used bromine-containing fire extinguishing agents which have been linked to the destruction of the earth""s ozone layer.
In other aspects, this invention also provides an extinguishing composition and a process for preventing fires in enclosed areas.
The present invention also provides novel fluoroketones of the formula (CF3)2CFC(O)CF2Cl and CF3OCF2CF2C(O)CF(CF3)2 and fire extinguishing compositions which include such novel fluoroketones in amounts sufficient to extinguish a fire.
The present invention also provides a process for reacting an acyl halide with hexafluoropropylene to make a fluorinated ketone having a minimal amount of dimer and trimer by-products.
The present invention further provides a process for removing undesired dimeric and/or trimeric by-products formed in the preparation of a fluorinated ketone prepared by the reaction of hexafluoropropylene with an acyl halide in the presence of fluoride ion where the reaction product, i.e., the fluorinated ketone, is treated with an alkali permanganate salt, e.g. potassium permanganate, in a suitable solvent.
Compounds that can be utilized in the processes and composition of the invention are fluorinated ketone compounds. The compounds of this invention can be utilized alone, in combination with one another, or in combination with other known extinguishing agents (e.g., hydrofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons, perfluoropolyethers, hydrofluoropolyethers, hydrofluoroethers, chlorofluorocarbons, bromofluorocarbons, bromochlorofluorocarbons, hydrobromocarbons, iodofluorocarbons, and hydrobromofluorocarbons). The compounds can be solids, liquids, or gases under ambient conditions of temperature and pressure, but are preferably utilized for extinguishing in either the liquid or the vapor state (or both). Thus, normally solid compounds are preferably utilized after transformation to liquid and/or vapor through melting, sublimation, or dissolution in a liquid co-extinguishing agent. Such transformation can occur upon exposure of the compound to the heat of a fire or flame.
Fluorinated ketones useful in this invention are ketones which are fully fluorinated, i.e., all of the hydrogen atoms in the carbon backbone have been replaced with fluorine; or ketones which are fully fluorinated except for one or two hydrogen, chlorine, bromine and/or iodine atoms remaining on the carbon backbone. Fire performance is compromised when too many hydrogen atoms are present on the carbon backbone. For example, a fluorinated ketone with three or more hydrogen atoms on the carbon backbone performs more poorly than a ketone with the same fluorinated carbon backbone but having two, one or zero hydrogen atoms, so that significantly more extinguishing composition of the former is required to extinguish a given fire. The fluoroketones may also include those that contain one or more catenated heteroatoms interrupting the carbon backbone in the perfluorinated portion of the molecule. A catenated heteroatom is, for example, a nitrogen, oxygen or sulfur atom.
Preferably, the majority of halogen atoms attached to the carbon backbone are fluorine; most preferably, all of the halogen atoms are fluorine so that the ketone is a perfluorinated ketone. More preferred fluorinated ketones have a total of 4 to 8 carbon atoms. Representative examples of perfluorinated ketone compounds suitable for use in the processes and compositions of the invention include CF3CF2C(O)CF(CF3)2, (CF3)2CFC(O)CF(CF3)2, CF3(CF2)2C(O)CF(CF3)2, CF3(CF2)3C(O)CF(CF3)2, CF3(CF2)5C(O)CF3, CF3CF2C(O)CF2CF2CF3, CF3C(O)CF(CF3)2 and perfluorocyclohexanone.
In addition to demonstrating excellent fire-fighting performance, the fluorinated ketones offer important benefits in environmental friendliness and can offer additional important benefits in toxicity. For example, CF3CF2C(O)CF(CF3)2 has low acute toxicity, based on short term inhalation tests with mice exposed for four hours at a concentration of 50,000 ppm in air. Based on photolysis studies at 300 nm, CF3CF2C(O)CF(CF3)2 has an estimated atmospheric lifetime of 3 to 5 days. Other fluorinated ketones show similar absorbances and are expected to have similar atmospheric lifetimes. As a result of their rapid degradation in the lower atmosphere, the perfluorinated ketones have short atmospheric lifetimes and would not be expected to contribute significantly to global warming.
Fluorinated ketones can be prepared by known methods, e.g., by dissociation of perfluorinated carboxylic acid esters by reacting the perfluorinated ester with a source of fluoride ion under reacting conditions, as described in U.S. Pat. No. 5,466,877 (Moore et al.), by combining the ester with at least one initiating reagent selected from the group consisting of gaseous, non-hydroxylic nucleophiles; liquid, non-hydroxylic nucleophiles; and mixtures of at least one non-hydroxylic nucleophile (gaseous, liquid, or solid) and at least one solvent which is inert to acylating agents. The fluorinated carboxylic acid ester precursors can be derived from the corresponding fluorine-free or partially fluorinated hydrocarbon esters by direct fluorination with fluorine gas as described in U.S. Pat. No. 5,399,718 (Costello et al.).
Fluorinated ketones that are alpha-branched to the carbonyl group can be prepared as described in, for example, U.S. Pat. No. 3,185,734 (Fawcett et al.) and J. Am. Chem. Soc., v. 84, pp. 4285-88, 1962. These branched fluorinated ketones are most conveniently prepared by hexafluoropropylene addition to acyl halides in an anhydrous environment in the presence of fluoride ion at an elevated temperature, typically at around 50 to 80xc2x0 C. The diglyme/fluoride ion mixture can be recycled for subsequent fluorinated ketone preparations, e.g., to minimize exposure to moisture. When this reaction scheme is employed, a small amount of hexafluoropropylene dimer and/or trimer may reside as a by-product in the branched perfluoroketone product. The amount of dimer and/or trimer may be minimized by gradual addition of hexafluoropropylene to the acyl halide over an extended time period, e.g., several hours. These dimer and/or trimer impurities can usually be removed by distillation from the perfluoroketone. In cases where the boiling points are too close for fractional distillation, the dimer and/or trimer impurity may be conveniently removed in an oxidative fashion by treating the reaction product with a mixture of an alkali metal permanganate in a suitable organic solvent such as acetone, acetic acid, or a mixture thereof at ambient or elevated temperatures, preferably in a sealed vessel. Acetic acid is a preferred solvent for this purpose; it has been observed that acetic acid tends not to degrade the ketone whereas in some instances some degradation of the ketone was noted when acetone was used. The oxidation reaction is preferably carried out at an elevated temperature, i.e., above room temperature, preferably from about 40xc2x0 C. or higher, to accelerate the reaction. The reaction can be carried out under pressure, particularly if the ketone is low boiling. The reaction is preferably carried out with agitation to facilitate complete mixing of two phases which may not be totally miscible.
When relatively volatile, short-chain acyl halides are employed (e.g., acyl halides containing from two to about five carbon atoms) in the hexafluoropropylene addition reaction, significant pressure build-up can occur in the reactor at elevated reaction temperatures (e.g., at temperatures ranging from about 50xc2x0 C. to about 80xc2x0 C.). It has been discovered that this pressure build-up can be minimized if only a fraction of the acyl halide charge (e.g., about 5 to 30 percent) is initially added to the reactor and the remaining portion of acyl halide is co-charged with the hexafluoropropylene continuously or in small increments (preferably in an equimolar ratio) over an extended time period (e.g., 1 to 24 hours, depending in part upon the size of the reactor). The initial acyl halide charge and the subsequent co-feeding to the reactor also serves to minimize the production of by-product hexafluoropropylene dimers and/or trimers. The acyl halide is preferably an acyl fluoride and may be perfluorinated (e.g., CF3COF, C2F5COF, C3F7COF), may be partially fluorinated (e.g., HCF2CF2COF), or may be unfluorinated (e.g., C2H5COF), with the product ketone formed being perfluorinated or partially fluorinated. The perfluoroketones may also include those that contain one or more catenated heteroatoms interrupting the carbon backbone in the perfluorinated portion of the molecule, such as, for example, a nitrogen, oxygen or sulfur atom.
Perfluorinated ketones which may be linear can be prepared according to the teachings of U.S. Pat. No. 4,136,121 (Martini et al.) by reacting a perfluorocarboxylic acid alkali metal salt with a perfluorinated acid fluoride. Such ketones can also be prepared according to the teachings of U.S. Pat. No. 5,998,671 (Van Der Puy) by reacting a perfluorocarboxylic acid salt with a perfluorinated acid anhydride in an aprotic solvent at elevated temperatures.
All of the above-mentioned patents describing the preparation of fluorinated ketones are incorporated by reference in their entirety.
The extinguishing process of the invention can be carried out by introducing a non-flammable extinguishing composition comprising at least one fluorinated ketone compound to a fire or flame. The fluorinated ketone compound(s) can be utilized alone or in a mixture with each other or with other commonly used clean extinguishing agents, e.g., hydrofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons, perfluoropolyethers, hydrofluoroethers, hydrofluoropolyethers, chlorofluorocarbons, bromofluorocarbons, bromochlorofluorocarbons, hydrobromocarbons, iodofluorocarbons, and hydrobromofluorocarbons. Such co-extinguishing agents can be chosen to enhance the extinguishing capabilities or modify the physical properties (e.g., modify the rate of introduction by serving as a propellant) of an extinguishing composition for a particular type (or size or location) of fire and can preferably be utilized in ratios (of co-extinguishing agent to fluorinated ketone compound(s)) such that the resulting composition does not form flammable mixtures in air. Preferably, the extinguishing mixture contains from about 10-90% by weight of at least one fluorinated ketone and from about 90-10% by weight of at least one co-extinguishing agent. Preferably, the fluorinated ketone compound(s) used in the composition have boiling points in the range of from about 0xc2x0 C. to about 150xc2x0 C., more preferably from about 0xc2x0 C. to about 110xc2x0 C.
The extinguishing composition can preferably be used in either the gaseous or the liquid state (or both), and any of the known techniques for introducing the composition to a fire can be utilized. For example, a composition can be introduced by streaming, e.g., using conventional portable (or fixed) fire extinguishing equipment; by misting; or by flooding, e.g., by releasing (using appropriate piping, valves, and controls) the composition into an enclosed space surrounding a fire or hazard. The composition can optionally be combined with inert propellant, e.g., nitrogen, argon, or carbon dioxide, to increase the rate of discharge of the composition from the streaming or flooding equipment utilized. When the composition is to be introduced by streaming or local application, fluorinated ketone compound(s) having boiling points in the range of from about 20xc2x0 C. to about 110xc2x0 C. (especially fluorinated ketone compounds which are liquid under ambient conditions) can preferably be utilized. When the composition is to be introduced by misting, fluorinated ketone compound(s) having boiling points in the range of from about 20xc2x0 C. to about 110xc2x0 C. are generally preferred. And, when the composition is to be introduced by flooding, fluorinated ketone compound(s) having boiling points in the range of from about 0xc2x0 C. to about 75xc2x0 C. (especially fluorinated ketone compound(s) which are gaseous under ambient conditions) are generally preferred.
Preferably, the extinguishing composition is introduced to a fire or flame in an amount sufficient to extinguish the fire or flame. One skilled in the art will recognize that the amount of extinguishing composition needed to extinguish a particular fire will depend upon the nature and extent of the hazard. When the extinguishing composition is to be introduced by flooding, cup burner test data (e.g., of the type described in the Examples, infra) can be useful in determining the amount or concentration of extinguishing composition required to extinguish a particular type and size of fire.
This invention also provides an extinguishing composition comprising (a) at least one fluorinated ketone compound; and (b) at least one co-extinguishing agent selected from the group consisting of hydrofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons, perfluoropolyethers, hydrofluoroethers, hydrofluoropolyethers, chlorofluorocarbons, bromofluorocarbons, bromochlorofluorocarbons, iodofluorocarbons, hydrobromofluorocarbons, and hydrobromocarbons. Representative examples of co-extinguishing agents which can be used in the extinguishing composition include CF3CH2CF3, C5F11H, C6F13H, C4F9H, CF3CFHCFHCF2CF3, H(CF2)4H, CF3H, C2F5H, CF3CFHCF3, CF3CF2CF2H, CF3CHCl2, CF3CHClF, CF3CHF2, CF4, C2F6, C3F8, C4F10, C6F14, C3F7OCH3, C4F9OCH3, F(C3F6O)CF2H, F(C3F6O)2CF2H, HCF2O(CF2CF2O)CF2H, HCF2O(CF2CF2O)2CF2H, HCF2O(CF2O)(CF2CF2O)CF2H, C2F5Cl, CF3Br, CF2ClBr, CF3I, CF2HBr, n-C3H7Br, and CF2BrCF2Br. (For a representative listing of known clean extinguishing agents, see NFPA 2001, xe2x80x9cStandard for Clean Agent Fire Extinguishing Systems,xe2x80x9d 2000 Edition, Table 1-5.1.2, p. 2001-5.) The ratio of co-extinguishing agent to fluorinated ketone is preferably such that the resulting composition does not form flammable mixtures in air (as defined by standard test method ASTM E681-85). The weight ratio of co-extinguishing agent to fluorinated ketone may vary from about 9:1 to about 1:9.
These fluorinated ketone compositions can be utilized in co-application processes with not-in-kind fire-fighting technologies to provide enhanced extinguishing capabilities. For example, the liquid composition CF3CF2C(O)CF(CF3)2 can be introduced into an aqueous film forming foam (AFFF) solution stream, for example, utilizing a Hydro-Chem(trademark) nozzle manufactured by Williams Fire and Hazard Control, Inc., Mauriceville, Tex. to give the AFFF three-dimensional fire-fighting capability. The AFFF can carry the CF3CF2C(O)CF(CF3)2 a much longer distance than it could be delivered by itself to a remote three dimensional fuel fire, allowing the CF3CF2C(O)CF(CF3)2 to extinguish the three-dimensional fuel fire where the AFFF stream by itself would not.
Another co-application process utilizing fluorinated ketones can be extinguishing a fire using a combination of a gelled halocarbon with dry chemical. A dry chemical can be introduced in suspension in the liquid CF3CF2C(O)CF(CF3)2 and discharged from a manual handheld extinguisher or from a fixed system.
Yet another co-application process utilizing fluorinated ketones is the process where the fluorinated ketone is super-pressurized upon activation of a manual hand-held extinguisher or a fixed system using an inert off-gas generated by the rapid burning of an energetic material such as glycidyl azide polymer. In addition, rapid burning of an energetic material such as glycidyl azide polymer that yields a hot gas can be used to heat and gasify a liquid fluorinated ketone of the invention or other liquid fire extinguishing agent to make it easier to disperse. Furthermore, an unheated inert gas (e.g., from rapid burning of an energetic material) might be used as to propel liquid fluorinated ketones of the invention or other liquid fire extinguishing agents to facilitate dispersal.
The above-described fluorinated ketone compounds can be useful not only in controlling and extinguishing fires but also in preventing the combustible material from igniting. The invention thus also provides a process for preventing fires or deflagration in an air-containing, enclosed area which contains combustible materials of the self-sustaining or non-self-sustaining type. The process comprises the step of introducing into an air-containing, enclosed area a non-flammable extinguishing composition which is essentially gaseous, i.e., gaseous or in the form of a mist, under use conditions and which comprises at least one fluorinated ketone compound containing up to two hydrogen atoms, optionally up to two halogen atoms selected from chlorine, bromine, iodine, and a mixture thereof, and optionally containing additional catenated heteroatoms, and the composition being introduced and maintained in an amount sufficient to impart to the air in the enclosed area a heat capacity per mole of total oxygen present that will suppress combustion of combustible materials in the enclosed area.
Introduction of the extinguishing composition can generally be carried out by flooding or misting, e.g., by releasing (using appropriate piping, valves, and controls) the composition into an enclosed space surrounding a fire. However, any of the known methods of introduction can be utilized provided that appropriate quantities of the composition are metered into the enclosed area at appropriate intervals. Inert propellants, such as those propellants generated by decomposition of energetic materials such as glycidyl azide polymers, can optionally be used to increase the rate of introduction.
For fire prevention, fluorinated ketone compound(s) (and any co-extinguishing agent(s) utilized) can be chosen so as to provide an extinguishing composition that is essentially gaseous under use conditions. Preferred compound(s) have boiling points in the range of from about 0xc2x0 C. to about 110xc2x0 C.
The composition is introduced and maintained in an amount sufficient to impart to the air in the enclosed area a heat capacity per mole of total oxygen present that will suppress combustion of combustible materials in the enclosed area. The minimum heat capacity required to suppress combustion varies with the combustibility of the particular flammable materials present in the enclosed area. Combustibility varies according to chemical composition and according to physical properties such as surface area relative to volume, porosity, etc.
In general, a minimum heat capacity of about 45 cal/xc2x0 C. per mole of oxygen is adequate to extinguish or protect moderately combustible materials (e.g., wood and plastics), and a minimum of about 50 cal/xc2x0 C. per mole of oxygen is adequate to extinguish or protect highly combustible materials (e.g., paper, cloth, and some volatile flammable liquids). Greater heat capacities can be imparted if desired but may not provide significantly greater fire suppression for the additional cost involved. Methods for calculating heat capacity (per mole of total oxygen present) are well-known (see, e.g., the calculation described in U.S. Pat. No. 5,040,609 (Dougherty et al.), the description of which is incorporated herein by reference in its entirety).
The fire prevention process of the invention can be used to eliminate the combustion-sustaining properties of air and to thereby suppress the combustion of flammable materials (e.g., paper, cloth, wood, flammable liquids, and plastic items). The process can be used continuously if a threat of fire always exists or can be used as an emergency measure if a threat of fire or deflagration develops.
Objects and advantages of this invention are further illustrated by the following examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this invention. Unless otherwise specified, all percentages and proportions are by weight.